Neurophysiologic and cognitive impairments have been reported in cocaine dependent patients abstaining from cocaine. The nature of these impairments have yet to be documented in a controlled clinical laboratory study. The present study monitors the subjective, psychiatric, cognitive and neurophysiologic status of cocaine dependent patient and the matched control subjects over a six to eight week period of abstinence. The control group is similar to the cocaine dependent patients in age, education and drug use history other than cocaine. The control group also controls for the effects of hospitalization and practice on the cognitive tasks. The EEG and cognitive information processing brain potentials were recorded from Fz, Cz, Pz, F3, F4, P3, P4, T3, T4, 01 and 02 scalp sites during three passive (Eyes Closed, Eyes open and Brainstem Auditory Evoked Response procedures) and seven active behavioral tasks (Auditory Rare event Monitoring Task, two Continuous Performance Tasks and four Sternberg Memory Tasks). Fourteen of the planned twenty subjects were tested in the previous year. Statistical analysis was performed in the current year. The amount and distribution of EEG beta (fast brain activity) in the cocaine dependent patients was significantly different than the control subject over the entire study. This EEG pattern may represent residual neurological alterations in cocaine dependent patients and may be a factor contributing to treatment relapse. The P300 brain component of the cocaine dependent subjects was reduced on the a visual and auditory cognitive task. Percent correct was on the Sternberg memory task was progressively poorer for the cocaine dependent individuals over the two month period of abstinence. Thus, the efficacy of treatment interventions for cocaine dependence my now be monitored by objective neurophysiological and performance measures.